Serial measurement of the circulating levels of tumour necrosis factor and its soluble receptors 1 and 2 for monitoring leprosy patients during multidrug treatment

Leprosy is an infectious and contagious spectral disease accompanied by a series of immunological events triggered by the host response to the aetiologic agent, Mycobacterium leprae . The induction and maintenance of the immune/inflammatory response in leprosy are linked to multiple cell interactions and soluble factors, primarily through the action of cytokines. The purpose of the present study was to evaluate the serum levels of tumour necrosis factor (TNF)-α and its soluble receptors (sTNF-R1 and sTNF-R2) in leprosy patients at different stages of multidrug treatment (MDT) in comparison with non-infected individuals and to determine their role as putative biomarkers of the severity of leprosy or the treatment response. ELISA was used to measure the levels of these molecules in 30 healthy controls and 37 leprosy patients at the time of diagnosis and during and after MDT. Our results showed increases in the serum levels of TNF-α and sTNF-R2 in infected individuals in comparison with controls. The levels of TNF-α, but not sTNF-R2, decreased with treatment. The current results corroborate previous reports of elevated serum levels of TNF-α in leprosy and suggest a role for sTNF-R2 in the control of this cytokine during MDT.     

Population Structure of Peronospora effusa in the Southwestern United States

Peronospora effusa is an obligate pathogen that causes downy mildew on spinach and is considered the most economically important disease of spinach. The objective of the current research was to assess genetic diversity of known historical races and isolates collected in 2014 from production fields in Yuma, Arizona and Salinas Valley, California. Candidate neutral single nucleotide polymorphisms (SNPs) were identified by comparing sequence data from reference isolates of known races of the pathogen collected in 2009 and 2010. Genotypes were assessed using targeted sequencing on genomic DNA extracted directly from infected plant tissue. Genotyping 26 historical and 167 contemporary samples at 46 SNP loci revealed 82 unique multi-locus genotypes. The unique genotypes clustered into five groups and the majority of isolates collected in 2014 were genetically closely related, regardless of source location. The historical samples, representing several races, showed greater genetic differentiation. Overall, the SNP data indicate much of the genotypic variation found within fields was produced during asexual development, whereas overall genetic diversity may be influenced by sexual recombination on broader geographical and temporal scales.     

Differential responses by two closely related native fishes to restoration actions

Globally, river degradation has decimated freshwater fish populations. To help reverse this trend in a southeastern Australia river, we used multiple restoration actions, including reintroduction of instream woody habitat, riparian revegetation, removal of a weir hindering fish movement, fencing out livestock, and controlling riparian weeds. We monitored the responses of native fish at the segment scale (20 km) and reach scale (0.3 km) over 7 years to assess the effectiveness of the different restoration strategies. Two closely related species, Murray cod Maccullochella peeli and trout cod Maccullochella macquariensis, increased at the restored segment compared with the control segment. However, inherent differences between river segments and low sample size hampered assessment of the mechanisms responsible for segment‐scale changes in fish abundance. In contrast, at the reach scale, only M. peeli abundance significantly increased in reaches supplemented with wood. These differential responses by 2 closely related fish species likely reflect species‐specific responses to increased habitat availability and enhanced longitudinal connectivity when the weir improved passage around a fishway. Changes in M. peeli abundance in segments supplemented with and without wood suggest an increase in carrying capacity and not simply a redistribution of individuals within the segment, facilitated the observed expansion. Our findings confirm the need to consider individual fish species' habitat preferences carefully when designing restoration interventions. Further, species‐specific responses to restoration actions provide waterway managers with precise strategies to target fish species for recovery and the potential to predict fish outcomes based on ecological preferences.     

A cysteine protease gene is expressed early in resistant potato interactions with Phytophthora infestans

A potato cysteine protease (cyp) cDNA expressed at an early stage of an incompatible interaction with Phytophthora infestans was isolated. Both the nucleotide and deduced amino acid sequences are highly homologous to those of a tomato cysteine protease, CYP1. Striking protein similarity to all known cathepsins in animals, particularly cathepsin K, was also observed. However, unlike cathepsins, a granulin binding domain is located near the carboxyl terminus of the putative CYP protein. In animals, granulins bind to receptors in the plasma membrane and signal cell growth and division. A ribonuclease protection assay demonstrated that the cyp gene is tightly regulated and is induced 15 h post inoculation with P. infestans in potato leaves either with high field resistance or in which a resistance (R) gene is activated. We conclude that a common signaling pathway is activated in each form of resistance.     

Structural basis of HP1/PXVXL motif peptide interactions and HP1 localisation to heterochromatin

HP1 family proteins are adaptor molecules, containing two related chromo domains that are required for chromatin packaging and gene silencing. Here we present the structure of the chromo shadow domain from mouse HP1beta bound to a peptide containing a consensus PXVXL motif found in many HP1 binding partners. The shadow domain exhibits a novel mode of peptide recognition, where the peptide binds across the dimer interface, sandwiched in a beta-sheet between strands from each monomer. The structure allows us to predict which other shadow domains bind similar PXVXL motif-containing peptides and provides a framework for predicting the sequence specificity of the others. We show that targeting of HP1beta to heterochromatin requires shadow domain interactions with PXVXL-containing proteins in addition to chromo domain recognition of Lys-9-methylated histone H3. Interestingly, it also appears to require the simultaneous recognition of two Lys-9-methylated histone H3 molecules. This finding implies a further complexity to the histone code for regulation of chromatin structure and suggests how binding of HP1 family proteins may lead to its condensation.     

James Neel and the doubling dose concept

The doubling dose (DD) is a very valuable concept in attempts to assess the genetic risks of radiation in man. It was long thought that the value of the doubling dose obtained from specific locus experiments in mice could be applied to man. James Neel, as a result of his studies on the offspring of atomic bomb survivors, showed that this was not so, but that different doubling doses could be inferred from different endpoints.     

Trigger factor-mediated prolyl isomerization influences maturation of the Streptococcus pyogenes cysteine protease

Trigger factor, a ribosome-associated chaperone and peptidyl-prolyl cis-trans isomerase (PPIase), is essential for the secretion and maturation of the cysteine protease of the pathogenic gram-positive bacterium Streptococcus pyogenes. In the absence of trigger factor, the nascent protease polypeptide is not targeted to the secretory pathway. Some partial-function mutations restore targeting. However, the secreted protease does not efficiently mature into an enzymatically active form, suggesting that trigger factor has an additional role in protease biogenesis. Here, we show that, while not required for targeting, the PPIase activity of trigger factor is essential for maturation of the protease following its secretion from the bacterial cell. Site-specific mutations introduced into ropA, the gene which encodes trigger factor in S. pyogenes, produced mutant proteins deficient in PPIase activity. When these mutant alleles were used to replace the wild-type gene on the streptococcal chromosome, analysis of protease biogenesis revealed that, although the protease was secreted normally, it did not efficiently mature to an active form. Furthermore, mutation of a single proline residue in the protease prodomain suppressed the requirement for PPIase activity, suggesting that this residue is the target of trigger factor. These data support a model in which trigger factor-mediated prolyl isomerization influences the conformation of the prodomain, which in turn directs the protease into one of several alternative folding pathways.